The art has heretofore known generally that shaped semiconductor bodies can be made by depositing a semiconductor material onto a heated carrier body at elevated temperatures in an appropriate atmosphere; see, for examples, Brit. Pat. No. 1,263,580 and W. Ger. Pat. No. 1,805,970.
The carrier body is heated to semiconductor deposition temperature either inductively or by the direct passage therethrough of an electric current.
In this way silicon tubes of the type useful in diffusion processes can be produced using silico-chloroform as the starting compound and temperatures from about 1050.degree. to 1250.degree. C. in a hydrogen atmosphere. The silicon tubes so produced have the advantage of a high degree of purity. The carrier body used for making such a silicon tube advantageously is made of graphite and is in a hollow form. This body, following such a deposition process, is then conveniently burned away by heating in an atmosphere containing oxygen.
In such a diffusion deposition process (see above-mentioned Brit. patent specification No. 1,263,580), the carrier body has been heated either by means of multi-turn induction heating coil which surrounds the deposition chamber, or, if the carrier body is of tubular shape, by means of a current conductor arranged in the interior of the carrier body, which conductor is connected in such a way that the carrier body is directly heated by an electric current.
The direct heating of graphite carrier bodies by a current has been found to have the significant disadvantage that the current is commonly not uniformly distributed over the cross-sectional area of the graphite body, and consequently the temperature distribution over the deposition surface is non-unform. Such semiconductor material deposition conditions leads to products of variable quality and of uncertain characteristics, while the production of semiconductor shaped bodies using directly heated carrier bodies which are of a complicated shape either cannot be carried out at all, or, at best, is so extremely expensive as to be commercially impractical. Furthermore, such a deposition procedure makes it difficult to produce semiconductor bodies of substantially uniform characteristics having a predetermined wall thickness.
In addition, such a direct carrier body heating technique commonly involves deposition of semiconductor material on the heater body (or heater element) commonly necessitating intermediate processing, and, typically, clean-up of such heater bodies before re-use. Indeed, sometimes the heater body itself may be used only once in some prior art embodiments.
Sometimes the heater body cannot be separated from the carrier body, or is at best only difficultly separable, which is a further problem in the prior art.
Moreover, such prior art heating technique in semiconductor deposition does not enable one to produce controlled temperature variations in the carrier body during deposition of semiconductor material thereon, such as is especially desired sometimes when making shaped bodies of semiconductor material having particular, non-uniform, cross-sectional configurations, including bodies with slots and holes.